Considering how much shit people have always got over evidence that "doesn't fit in with ... anything", how surprising is it that you mostly only know about evidence that does?
The null hypothesis is always that mammals go where they can. Period. You need an explanation for any circumstance when they evidently couldn't go somewhere. It doesn't matter what fits your preconceptions and biases. Humans are mammals.
People got to Crete 200,000 years ago. By boat. Were they H. erectus? H. n.? H. sap.? Nobody knows. People got to Australia 70kya. By boat. We are pretty sure those were H. sap. Anybody who can get to Australia, sailing out of sight of land, can get to lots of other places just as easily: the Philippines, Japan, the Aleutians, etc. Particularly when sea level is 120m lower.
The null hypothesis (if that's even a good one, which I'm unconvinced about, but whatever considering we see plenty of animals that have evolved in the same area without leaving it) is not some ultimate arbiter of what's true. I don't know why you keep referring to it like your claim must be true because it's your null hypothesis or something.
The null hypothesis is that 2 variables are uncorrelated. You can't just call your hypothesis "the null hypothesis" to try to make it sound more likely.
It is a matter of where the burden of proof legitimately is, and what evidence you need to bring.
If you think humans were blocked from access to North America, you need a mechanism to have blocked them, and evidence for it. We know that the fossil record is absurdly thin, and get our noses rubbed in it each generation, but seem never to learn better.
The null hypothesis is always that mammals go where they can. Period. You need an explanation for any circumstance when they evidently couldn't go somewhere. It doesn't matter what fits your preconceptions and biases. Humans are mammals.
People got to Crete 200,000 years ago. By boat. Were they H. erectus? H. n.? H. sap.? Nobody knows. People got to Australia 70kya. By boat. We are pretty sure those were H. sap. Anybody who can get to Australia, sailing out of sight of land, can get to lots of other places just as easily: the Philippines, Japan, the Aleutians, etc. Particularly when sea level is 120m lower.